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C Chapman

Publications and source records attributed to C Chapman.

At least 37 records · Page 2Linked to original sources
PubMed1996

Analysis of immunoglobulin variable region genes of a human IgM anti-myeloperoxidase antibody derived from a patient with vasculitis.

Circulating antibodies to myeloperoxidase (MPO) are associated primarily with pauci-immune glomerulonephritis and systemic vasculitis. Anti-MPO antibodies belong to a group of autoantibodies, anti-neutrophil cytoplasmic antibodies, that may play a pathogenic role in vasculitis. We have generated a human monoclonal anti-MPO antibody (E3-MPO) using peripheral blood lymphocytes from a patient with microscopic polyarteritis. Variable region gene analysis of E3-MPO showed that the VH region had 90% homology with the germ line gene VH4-21. E3-MPO was also shown to carry the 9G4 idiotope, which so far has been associated only with human antibodies that utilize the VH4-21 gene. The 9G4 idiotope was also expressed on anti-MPO antibodies in sera from the donor patient and from 4/7 additional patients with active, untreated vasculitis. The nucleotide sequences of both the variable heavy and light chains of E3-MPO showed evidence of an antigen-driven response.

Adult↗
PubMed1996

Effects of central GABAB receptor modulation upon the milk ejection reflex in the rat.

In order to investigate the role of central GABAB receptors in the control of the milk ejection reflex, we have examined the effects of third ventricular and bilateral supraoptic nucleus (SON) injections of a GABAB receptor agonist (baclofen) and antagonist (hydroxy-saclofen) on the milk ejection reflex in the urethane-anaesthetised rat. In addition, microdialysis studies have evaluated whether the activation of GABAB receptors in the SON is able to modulate the release of GABA and glutamate, two major neurotransmitters involved in the regulation of the milk ejection reflex. Intracerebroventricular injections of baclofen (n = 9) in doses of 10, 50 and 100 pmol inhibited the milk ejection reflex in a dose-dependent manner, without affecting the electroencephalogram or attenuating the intramammary pressure response to intravenous injection of 0.5 mU exogenous oxytocin. Hydroxy-saclofen given into the third ventricle in doses of 100 pmol (n = 2) and 500 pmol (n = 4) did not modify the pattern of the milk ejection reflex. Bilateral SON microinfusions of baclofen in doses of 80 (n = 2) and 200 pmol (n = 4) did not modify the pattern of the milk ejection reflex. In microdialysis experiments (n = 8), inclusion of baclofen into the microdialysate at a concentration of 500 microM had no effect upon basal or potassium-stimulated GABA and glutamate outflow. These results show that the activation of GABAB receptors located outside, but not within, the SON are capable of inhibiting the milk ejection reflex. In contrast to our previous findings regarding the GABAA receptor, we found no evidence for a tonic role of GABAB receptors within the neural network inducing the periodic synchronous bursting of oxytocin neurons during suckling.

Animals↗
PubMed1996

Meal frequency; does it determine postprandial lipaemia?

OBJECTIVE: To determine the effect of altering meal frequency on postprandial lipaemia and associated parameters. DESIGN: A randomized open cross over study to examine the programming effects of altering meal frequency. A standard test meal was given on three occasions following: (i) the normal diet; (ii) a period of two weeks on a nibbling and (iii) a period of two weeks on a gorging diet. SETTING: Free living subjects associated with the University of Surrey. SUBJECTS: Eleven female volunteers (age 22 +/- 0.89 y) were recruited. INTERVENTIONS: The subjects were requested to consume the same foods on either a nibbling diet (12 meals per day) or a gorging diet (three meals per day) for a period of two weeks. The standard test meal containing 80 g fat, 63 g carbohydrate and 20 g protein was administered on the day prior to the dietary intervention and on the day following each period of intervention. MAJOR OUTCOME MEASURES: Fasting and postprandial blood samples were taken for the analysis of plasma triacylglycerol, non-esterified fatty acids, glucose, immunoreactive insulin, glucose-dependent insulinotropic polypeptide levels (GIP) and glucagon-like peptide (GLP-1), fasting total, low density lipoprotein (LDL)- and high density lipoprotein (HDL)-cholesterol concentrations and postheparin lipoprotein lipase (LPL) activity measurements. Plasma paracetamol was measured following administration of a 1.5 g paracetamol load with the meal as an index of gastric emptying. RESULTS: The compliance to the two dietary regimes was high and there were no significant differences between the nutrient intakes on the two intervention diets. There were no significant differences in fasting or postprandial plasma concentrations of triacylglycerol, non-esterified fatty acids, glucose, immunoreactive insulin, GIP and GLP-1 levels, in response to the standard test meal following the nibbling or gorging dietary regimes. There were no significant differences in fasting total or LDL-cholesterol concentrations, or in the 15 min postheparin lipoprotein lipase activity measurements. There was a significant increase in HDL-cholesterol in the subjects following the gorging diet compared to the nibbling diet. DISCUSSION: The results suggest that previous meal frequency for a period of two weeks in young healthy women does not alter the fasting or postprandial lipid or hormonal response to a standard high fat meal. CONCLUSIONS: The findings of this study did not confirm the previous studies which suggested that nibbling is beneficial in reducing the concentrations of lipid and hormones. The rigorous control of diet content and composition in the present study compared with others, suggest reported effects of meal frequency may be due to unintentional alteration in nutrient and energy intake in previous studies.

Adult↗
PubMed1995

Family with partial monosomy 10p and trisomy 10p.

We report on a family with an abnormality of 10p. The propositus has monosomy for the distal region of 10p and severe psychomotor delay, growth failure, congenital heart defect, multicystic kidney, grade V vesicoureteric reflux, and neurosensory hearing loss. The mother and the elder brother of the propositus carry a balanced reciprocal translocation (5q;10p)(q35.3;p12.3). A retarded and epileptic maternal aunt was found to have dup(10p). Study of the family history led to the successful obstetric management of a subsequent twin pregnancy in which an affected fetus with dup(10p) was identified and selectively terminated, while the other normal twin was delivered at term without problems.

Abnormalities, Multiple↗
PubMed1995

Structural analysis of VH4-21 encoded human IgM allo- and autoantibodies against red blood cells.

We have sequenced the variable heavy chain regions of a number of VH4-21 encoded monoclonal IgM anti-Rh(D) antibodies produced in response to deliberate immunization. These were compared with the sequences of similarly encoded IgM anti-I cold agglutinins (CA) derived from patients with lympho-proliferative diseases. The anti-Rh(D) antibodies show evidence of clonal expansion and somatic diversification. Even though they are produced in response to an antigenic stimulus, they demonstrate limited hypermutation in the variable heavy chain (VH) segments and there is no evidence of selective pressure acting on the complementarity determining regions (CDRs). The CA demonstrate a higher rate of mutation and yet this results in a lower ratio of replacement to silent mutations (R:S) in the CDRs than seen in the anti-Rh(D) antibodies. It is not clear whether the different pattern of mutations seen in the CA is related to their auto-reactivity or their tumour origin. In both groups of antibodies the region encoded by the VH4-21 segment can be found in germline configuration at the amino-acid level indicating that other V-gene structures, i.e. light chains or CDRH3s, are crucial to the generation of either specificity. A role of the CDRH3 is indicated by the identification of a motif shared by four CAs and one Rh(D) antibody which also demonstrates CA activity independent of its anti-Rh(D) specificity. Amongst the anti-Rh(D) antibodies there seems to be an obligatory combination with VL having closest homology to the DPL16 germline segment indicating this as particularly important in generation anti-Rh(D) specificity.

Agglutinins↗
PubMed1995

Analysis of three new idiotypes on human monoclonal autoantibodies.

We have identified and characterised three new idiotypes on human IgM McAbs generated from the splenocytes of a SLE patient with active disease. RT-6, which binds H1 and Sm/RNP, expresses essentially a private Id. Its expression is limited to a small number of human McAbs and the sera from patients with infectious diseases. In contrast RT-72Id and RT-84Id, expressed on McAbs which are polyreactive for two or more antigens, have a public distribution. RT-72Id and RT-84Id are found on McAbs from murine and human adult, and foetal tissues. In sera, significant numbers of SLE, RA and patients with other autoimmune diseases are positive for both Ids. RT-84Id is also elevated in SLE relatives and spouses, and in patients with Klebsiella infection. No correlation with disease activity, IgM or IgG levels was observed with either Id. However, RT-72Id was significantly associated with anti-ssDNA antibodies and RhF. RT-6Id and RT-72Id are located on the framework regions of the mu heavy chain, whereas RT-84Id is present on the kappa light chain, within the binding site. The McAbs are encoded by mainly germline genes: heavy chains of RT-6, RT-72 and RT-84 are encoded by the genes VH26, VH4.22 and VH4.21, respectively, and the light chain sequences of RT-6 and RT-72 are derived from DPL11 and HK102. Immunofluorescent staining revealed the presence of RT-72Id and RT-84Id positive immunoglobulin deposits in 18% and 45%, respectively, of the lupus renal sections compared with none in the disease control group, suggesting that these Ids may contribute to the pathology of the disease.

Adult↗
PubMed1995

The utility of the CCK DISIDA scan in the treatment of occult biliary tract disease.

The vast majority of biliary tract disease is correlated with calculi, and the diagnosis of biliary disease is made simpler when calculi are detected. There are good screening studies for the detection of calculi; however, a reproducible objective test for biliary tract disease in the absence of gallstones has been lacking. Occult biliary tract disease should be considered when symptoms typical of biliary tract disease are present, gallstones cannot be demonstrated, and other diseases have been ruled out. This is characteristically a diagnosis of exclusion, with only the subjective criteria of pain relief to validate surgical intervention. Recently, we have used a nuclear medicine test that simulates the gallbladder response to normal postprandial physiologic stress, to study in an objective fashion the gallbladder function of a group of patients who have symptoms typical of biliary tract disease, but no demonstrable calculi. We have found that the CCK DISIDA study has correlated well with occult pathology. The experience at Easton Hospital has confirmed that the CCK augmented DISIDA scan with calculation of ejection fraction is a reasonably accurate study, with a sensitivity of 88% in detecting previously suspected but undemonstrable pathology in this selected population. This corresponds closely to the observed finding that the pathology reports of 77% of the resected gallbladders noted some abnormality. Of further interest is the long term symptomatic relief achieved in 85% of the patients available for follow up interviews, including a symptomatic benefit in eight of the 11 patients with a normal pathology report.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1995

Regulation of GABA transporter activity and mRNA expression by estrogen in rat preoptic area.

This study has examined whether estrogen regulates GABA transporter synthesis and activity in the female rat brain. In the first experiment in situ hybridization studies examined the effects of ovariectomy on cellular GABA transporter-1 (GAT-1) mRNA content. A 25% decrease in GAT-1 mRNA expression was detected within the medial preoptic area (MPOA) but not the parietal cortex, magnocellular preoptic nucleus (Mg-POA) or caudate-putamen (C-P). Estrogen replacement for 7 d returned GAT-1 mRNA content of MPOA cells to levels observed in intact rats. In the second experiment, the effect of increased brain GABA concentrations on GAT-1 mRNA expression was investigated by treating rats with gamma-vinyl GABA, a GABA-transaminase inhibitor. Although resulting in a twofold increase in tissue GABA content, in situ hybridization experiments revealed no changes in GAT-1 transcript expression. A third series of experiments examined GABA transporter activity in vitro using a 3H GABA uptake assay in MPOA, cortex, and C-P punches. Nipecotic acid (10 microM) reduced specific 3H GABA uptake in all three brain regions while 100 microM beta-alanine only reduced uptake in the MPOA. Estrogen treatment for 7 d resulted in a significant increase in 3H GABA uptake in the MPOA but not the cortex or C-P. The presence of a putative estrogen response element in the GAT-1 gene and the effects demonstrated here on GAT-1 mRNA content and GABA transporter activity indicate that estrogen may influence GAT-1 gene transcription to alter GABA transporter function within the MPOA but not the C-P or cortex.

4-Aminobutyrate Transaminase↗
PubMed1994

Beta 3-adrenoceptor agonist-induced down-regulation of Gs alpha and functional desensitization in a Chinese hamster ovary cell line expressing a beta 3-adrenoceptor refractory to down-regulation.

Chinese hamster ovary (CHO) cells transfected to express human beta 2- or beta 3-adrenoceptors (beta 2-CHO and beta 3-CHO cells) were exposed to the beta-adrenoceptor agonist isoprenaline at various concentrations and for differing times. Sustained exposure of the beta 2-CHO but not beta 3-CHO cells to isoprenaline resulted in a time- and concentration-dependent down-regulation of the receptor as measured by a reduction in specific binding of [125I]cyanopindolol. Such maintained exposure of cells expressing either receptor to the agonist produced a marked down-regulation of immunologically detectable levels of the alpha subunit of the stimulatory guanine-nucleotide-binding protein Gs. This effect was specific for Gs because levels of both G12 alpha and Gq alpha/G11 alpha were unaltered by isoprenaline treatment of both beta 2-CHO and beta 3-CHO cells. The effect of isoprenaline on Gs alpha down-regulation was some 30-fold more potent in the beta 2-CHO than in the beta 3-CHO cells. Time courses of isoprenaline-induced down-regulation of Gs alpha were not different, however, in the two cell lines. Isoprenaline treatment of the beta 3-CHO cells produced a desensitization of agonist-mediated regulation of adenylyl cyclase, manifested by a 4-fold reduction in the potency and a 30% reduction in maximal effect of the agonist, whereas desensitization of the beta 2-CHO cells was considerably greater (25-fold reduction in potency and 70% reduction in maximal effect). These results demonstrate that agonist-induced down-regulation of the G-protein which interacts with a receptor can be produced by both beta 2- and beta 3-adrenoceptors. Despite apparent concurrence of down-regulation of receptors and G-proteins in other systems [e.g. Adie, Mullaney, McKenzie and Milligan (1992) Biochem. J. 285, 529-536], agonist-induced receptor down-regulation does not appear to be a prerequisite for down-regulation of the G-protein. Furthermore, the results suggest that agonist-induced down-regulation of a G-protein may be sufficient, in the absence of receptor regulation, to induce some agonist desensitization of effector function.

Amino Acid Sequence↗
PubMed1994

A novel family of cathepsin L-like (CTSLL) sequences on human chromosome 10q and related transcripts.

We have isolated a human genomic DNA cosmid clone while screening for the cathepsin L gene that, when sequenced, revealed close similarity with but significant differences from cDNA sequences that have been reported for cathepsin L (CTSL). The clone bears a novel sequence that shows 88% identity to the coding regions of the cathepsin L gene and a similar exon arrangement. We have called this sequence the "human cathepsin L-like gene 1" (CTSLL1). Translating putative exon sequences reveals a single premature stop codon; therefore no functional products are likely to arise from this gene. Fluorescence in situ hybridization (FISH) studies mapped the clone to chromosome 10q. Somatic cell hybrid mapping confirmed the location of CTSLL1 to human chromosome 10 distinct from the cathepsin L locus (CTSL) on chromosome 9. Furthermore, the FISH mapping studies show that a family of at least three related sequences exists on chromosome 10q, similar to the pattern of duplicated glutamate dehydrogenase (GLUD) gene loci reported on 10q. Using PCR and sequencing with genomic DNA samples, we have identified two additional novel related sequences (CTSLL2 and CTSLL3), and by PCR analysis of cDNA samples we have identified corresponding transcripts. Comparison of changes between our CTSLL1 sequence and the cathepsin L gene at mutation insensitive sites suggests that the two sequences arose from a duplication event 40-50 million years ago, and therefore at the time of divergence of early primates.

Amino Acid Sequence↗
PubMed1994

Extracellular GABA concentrations in rat supraoptic nucleus during lactation and following haemodynamic changes: an in vivo microdialysis study.

Morphological and pharmacological evidence suggest that the dense GABAergic innervation of the supraoptic nucleus is important for regulating the electrical activity of vasopressin and oxytocin neurons. We have employed the technique of intracranial microdialysis to examine extracellular GABA concentrations in the supraoptic nucleus of the anaesthetized rat and questioned whether differences exist in the dynamics of GABA release between virgin and lactating rats, and if events during lactation or following blood pressure manipulation alter endogenous GABA levels in this nucleus. No significant differences were detected between virgin and lactating animals in either basal or 100 mM potassium ion-evoked GABA release. The inclusion of the GABA uptake blocker nipecotic acid (0.5 mM) into the dialysate resulted in a six- to eight-fold increase (P < 0.01) in GABA outflow in both groups of animals. In lactating rats, GABA outflow measured at 4 min intervals was not altered during a 60 min period of suckling by a full litter of pups and no significant change in GABA outflow was detected in relation to individual milk ejections. In virgin rats, removal of 1.5-2 ml of blood resulted in a 30-60 mmHg fall in blood pressure and a non-significant decline in GABA outflow. Replacement of blood resulted in an abrupt 50 mmHg increase in blood pressure and a significant 22% increase in GABA outflow (P < 0.01), but no change in aspartate or methionine concentrations. Repeated intravenous injections of the alpha-adrenoceptor agonist, metaraminol, similarly evoked approximately 50 mmHg increments in blood pressure and a 26% increase in GABA outflow (P < 0.05). Electrical stimulation of the diagonal band of Broca for 10 min produced a two-fold increase in GABA outflow from the supraoptic nucleus (P < 0.05). These results show that the overall profile of basal and potassium-stimulated GABA concentrations in the supraoptic nucleus is not substantially different between lactating and virgin rats. In lactating animals we have found that GABA levels are not altered in response to suckling or at the time of high-frequency firing by oxytocin neurons to induce milk ejection. In contrast, our data further support the hypothesis that GABA inputs to supraoptic neurons are part of a baroreceptor reflex, relaying through the diagonal band of Broca, to signal periods of acute hypertension and inhibit the firing of vasopressin neurons. Such observations suggest the physiological importance of GABA inputs to the supraoptic nuclei and indicate that GABA may be used in a stimulus-specific manner to influence the activity of magnocellular neurons.

Animals↗
PubMed1994

Stimulus-induced depletion of pro-enkephalins, oxytocin and vasopressin and pro-enkephalin interaction with posterior pituitary hormone release in vitro.

The secretion of oxytocin (OXT) from the neurohypophysis is modulated by the actions of opioids acting via kappa-receptors. The vasopressin (AVP)-containing nerve terminals in the neurohypophysis contain the kappa-opioid agonist dynorphin, but endogenous opioid restraint of OXT secretion is observed even when AVP release is not activated, suggesting that another source of opioids is responsible for modulating OXT secretion. We now report that acute stimulation of the rat neural lobe in vivo results in depletion of the neural lobe content of OXT, AVP, dynorphin A1-17, dynorphin A1-8 and metenkephalin (Met-Enk). The dynorphin content is depleted to a similar extent as that of OXT and AVP; a correlation analysis suggests that while most dynorphin is co-secreted with AVP, a significant portion is co-secreted with OXT, consistent with a co-localisation of dynorphin with OXT. Met-Enk was depleted to a lesser extent than either hormone, consistent with a partial localisation in non-releasable pools. However, depletion of Met-Enk was also observed following naloxone-precipitated opioid withdrawal accompanying selective hypersecretion of OXT, suggesting co-secretion of OXT and Met-Enk. Met-Enk is a mu-opioid receptor agonist, but extended forms of Met-Enk, as we now report, are active at neurohypophysial kappa-receptors.

Animals↗
PubMed1993

Pharmacologic induction of posterior vitreous detachment in the rabbit.

OBJECTIVE: To assay the proteolytic activity of plasmin on the vitreoretinal junction and to assess a potential facilitating effect on posterior vitreous detachment. METHODS: We injected 1 U of plasmin into the vitreous of rabbits. Some eyes underwent vitrectomy after plasmin injection. Electroretinography and electron microscopy were performed. RESULTS: In plasmin-treated eyes, electroretinography displayed a transient (3 days) decreased b-wave amplitude. Histologic examination demonstrated posterior vitreous detachment in eyes that received intravitreal plasmin followed by vitrectomy. CONCLUSION: Plasmin may prove to be a useful biochemical adjunct to mechanical vitrectomy.

Animals↗
PubMed1993

Gene mutations and increased levels of p53 protein in human squamous cell carcinomas and their cell lines.

Using immunocytochemical and Western blotting techniques we have demonstrated the presence of abnormally high levels of p53 protein in 8/24 (33%) of human squamous cell carcinomas (SCC) and 9/18 (50%) of SCC cell lines. There was a correlation between the immunocytochemical results obtained with eight SCC samples and their corresponding cell lines. Direct sequencing of PCR-amplified, reverse transcribed, p53 mRNA confirmed the expression of point mutations in six of the positive cell lines and detected in-frame deletions in two others. We also detected two stop mutations and three out-of-frame deletions in five lines which did not express elevated levels of p53 protein. Several of the mutations found in SCC of the tongue (3/7) were in a region (codons 144-166) previously identified as being a p53 mutational hot spot in non-small cell lung tumours (Mitsudomi et al., 1992). In 11/13 cases only the mutant alleles were expressed suggesting loss or reduced expression of the wild type alleles in these cases. Six of the mutations were also detected in the SCCs from which the lines were derived, strongly suggesting that the mutations occurred, and were selected, in vivo. The 12th mutation GTG-->GGG (valine-->glycine) at codon 216 was expressed in line SCC-12 clone B along with an apparently normal p53 allele and is to our knowledge a novel mutation. Line BICR-19 also expressed a normal p53 allele in addition to one where exon 10 was deleted. Additionally 15 of the SCC lines (including all of those which did not show elevated p53 protein levels) were screened for the presence of human papillomavirus types 16 and 18 and were found to be negative. These results are discussed in relation to the pathogenesis of SCC and the immortalisation of human keratinocytes in vitro.

Base Sequence↗